Miocene to Pleistocene explosive volcanism offshore Costa Rica; evidence for different sources from IODP Exp. 334, 344 and ODP Exp. 170

Author(s): Schindlbeck, J. C.; Kutterolf, S.; Straub, S. M.; Baxter, Alan T.; Sandoval Gutierrez, Maria Isabel; Stroncik, Nic; Wang, K.
Author Affiliation(s): Primary:
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Other:
Lamont-Doherty Earth Observatory, United States
University of New England, Australia
Université de Lausanne, Switzerland
GFZ, Germany
Academia Sinica, Taiwan
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: During IODP expeditions 334 and 344, offshore the Osa Peninsula, a total of 81 and 37 tephra layers were recovered at incoming plate Sites U1381 and U1414, on the flank of the Cocos Ridge, respectively. Additionally, 63 tephras were sampled near the Nicoya Peninsula during Leg 170. The ages of the marine tephras cover the whole range from Late Miocene to Late Pleistocene and single tephra layers can be correlated between Holes, Sites and Legs. Although they are in close proximity to each other (30 to 250 km), the Sites show strong variations in their tephra abundance and composition especially in glass shard color (transparent versus brown); grain size (silt versus sand size) and mineral assemblage (predominantly hornblende and biotite versus pyroxene and feldspar dominated). Within the first 56 mbsf at Site U1381, eighteen whitish to gray tephra layers are intercalated with hemipelagic Pleistocene sediments associated with a near trench depositional environment. In contrast, the 63 predominantly black tephra layers (>80%) recovered from >56 mbsf are embedded, below a >9 my hiatus, in a succession of sediments dominated by Miocene silicic and calcareous ooze. At Site U1414 (30 km NW away from Site U1381) and Site U1039 (Leg 170; 250 km NW away from Site U1381) a continuous sedimentary succession was recovered that encompasses the interval from the Holocene to the Middle Miocene. Tephra layers from Site U1414 are predominantly felsic in composition (>90%) and mafic tephras are less abundant than at Site U1381. Despite this difference, the appearance of the individual tephra layers and their glass shard and mineral inventory reflect the same variability as at Site U1381. At Site U1039 black mafic and grey to white felsic tephras are more evenly distributed with one third and two third, respectively. A preliminary provenance analysis based on major and trace elements suggests that most of the Pleistocene tephra layers were derived from Central American Volcanic Arc (CAVA) eruptions. We have been able to correlate marine tephras to major CAVA eruptions, from Costa Rica to Guatemala. In contrast, Miocene mafic and felsic tephras of Sites U1381 and U1039, respectively, show a mantle plume signature similar to the Galapagos mantle plume (e.g. high incompatible element concentrations; Nb, Ta trough in spider diagrams; La/Nb=≤1 is much lower than in CAVA volcanism), although the individual tephra compositions deviate slightly between both Sites. This may be due to regional variations observed in the Galapagos mantle plume source. Surprisingly, and despite its proximity to U1381, the trace element compositions of the entire tephra inventory of Site U1414 from Pleistocene to Miocene and of the Pliocene to Pleistocene portion of Site U1039 reflect arc-related explosive volcanism with different proportions of a mantle plume signal. This mixing signal is probably caused by recycling of ocean island basalts. How, where, when and to what extent the explosive volcanism along the Arc and the deposits at the respective drill sites have been influenced by hot spot volcanism will be investigated by means of trace element analyses, isotope data and Ar/Ar ages.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; Central America; Cocos Ridge; Costa Rica; Costa Rica Seismogenesis Project; East Pacific; Expedition 334; Expedition 344; Explosive eruptions; IODP Site U1381; IODP Site U1414; Igneous rocks; Integrated Ocean Drilling Program; Leg 170; Miocene; Neogene; North Pacific; Northeast Pacific; Ocean Drilling Program; Osa Peninsula; Pacific Ocean; Pleistocene; Pliocene; Pyroclastics; Quaternary; Tertiary; Volcanic rocks; Volcanism
Coordinates: N083014 N083014 W0841332 W0841332
N082543 N082543 W0840928 W0840929
Record ID: 2015006423
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